1. Field of the Invention
This invention relates to an ink jet recording method for a recording device equipped with a head having a plurality of nozzles corresponding to the respective ink colors of detractive color mixing of color recording to be used for example, in color ink jet recording device.
2. Related Background Art
FIG. 1 is a schematic upper view of an example of an ink jet recording device in general, FIG. 2 is a block diagram showing its control system.
FIG. 1, numeral 1 is a platen which rotates at predetermined steps for sub-scanning during recording with a recording medium (not shown) wound therearound. Numeral 2 is a line feed motor which transmits rotation to the rotational shaft of the platen 1 through a gear 3. 4 is an ink jet recording head (hereinafter called "head") mounted freely slidable on a guide bar (not shown) arranged in parallel to the platen 1, and is provided with a plurality of discharge openings 5 for discharging ink as droplets. Numeral 6 is a belt for moving the head 5 reciprocally in the longitudinal direction of the platen 1. Numerals 7 and 8 are pulleys arranged at the both ends of the belt 6, and numeral 9 a carriage motor for rotating the pulley 8.
Numeral 10 is a paper sensor for detecting the presence of a recording medium arranged in the vicinity of the surface of the platen 1, numeral 11 an encoder sensor mounted on the head 4, and numeral 12 a linear encoder fixedly arranged in parallel to the platen 1 and also opposed to the encoder sensor 11. Numeral 13 is a home position sensor for detecting that the head 4 is in the home position, numeral 14 is a cap which is used when restoring poor discharge including non-discharge, numeral 15 a motor which is the driving source for progressing forward and backward the cap 14 with respect to the head, and numeral 16 a cap sensor for detecting that the cap 14 is mounted on the head 4.
In the above constitution, when the recording medium is mounted on the platen 1, it is detected by the paper sensor 10 to be made in a recordable state. When the recording start button is pushed the carriage is moved, and the head 4, after being set at the home position, moves following the printing format of the recording device, and permits ink droplets to fly following the recording data from the discharge openings. The head 4 is subjected to main scanning, driven by the belt 6 with the motor 9 as the driving source. Every time when one line of main scanning is completed, the motor 2 is driven to rotate the platen 1.
For preventing clogging of the discharge openings of the head 4, the cap 14 is covered over the head 4 periodically or if necessary. This state is detected by the cap sensor 16, and recording actuation is intermitted by this detection. The restoration actuation comprises absorbing the ink within the nozzles from outside of the nozzles by an absorbing mechanism (not shown) communicated to the cap 14, thereby removing foreign matters, etc. within the nozzles. By doing so, subsequent defective recording will be cancelled.
Next, the constitution of the control system shown in FIG. 2 is to be described.
CPU 20 constitutes the main body of control, to which a group of switches 21 (arranged on the operational panel) are connected through an input and output interface (not shown), a DC servo reversing circuit 22 for driving the carriage motor 9, a stepping motor driving circuit 23 for driving the line feed motor 2, a head driver 24 for driving the recording head 4 based on the recording data, a group of various sensors 25, the encoder sensor 11 and the home position sensor 13.
In the constitution shown in FIG. 2, CPU 20 performs the following operational actuation corresponding to the operational input performed by the switch group 21 provided on the operational panel (not shown). More specifically, by referring to the input from the encoder sensor 11 and the home position sensor 13, the driving control of the carriage motor 9 is conducted through the DC servo reversing circuit 22, and also the driving control of the line feed motor 2 through the stepping motor driving circuit 23, whereby the recording data D is output to the head driver 24 and the recording head 4 is driven with the head driver 24. Also, control of other mechanisms is conducted corresponding to the inputs from another group of sensors 25.
Under such constitution, recording actuation is commenced by pushing down of the print switch among the switch group 21, and the line feed motor is driven several steps on confirmation of the presence of recording paper by the paper sensor 10, whereby the platen 1 is rotated and the recording paper set at the recording start position. Subsequently, the carriage motor 9 is driven to move the recording head 4 in a reciprocating manner, and the line feed motor 2 is driven as synchronized therewith to deliver the recording paper line by line. During such actuation, driving signals corresponding to the recording data are applied from the head driver 24 on the recording head 4 to drive the recording head 4, whereby ink is discharged as droplets through the discharge openings of the nozzles 5 to effect recording of letters, images, etc.
FIG. 3 is a schematic front view of the head 4 in FIG. 1.
As shown in FIG. 3, four discharge openings 41, 42, 43 and 44 are arranged at predetermined intervals on the same line. To the openings 41 to 44 the ink of cyan (C), magenta (M), yellow (Y) and black (BK) are sequentially supplied. At the respective ink path communicated with the discharge opening, energy generating members generating energy for discharging ink are mounted, which may comprise piezoelectric elements, etc. (not shown), and by applying predetermined voltages to the piezoelectric element, ink is discharged through the openings as droplets. To each of the openings 41 to 44 a pressure chamber in the shape of a pipe (not shown) is individually communicated, and each pressure chamber is communicated through a vinyl pipe, etc., to an ink tank containing the color ink corresponding to that opening.
In this case, as shown in FIG. 4, for the input signal, first a voltage Vrev of negative polarity is generated for a time period T1, which voltage is applied on the piezoelectric element to expand the pressure chamber. Next, a positive voltage Vop is generated for a time period T2, which is applied on the piezoelectric element to reduce the pressure chamber, thereby discharging the ink as the droplets. Further, the application voltage is gradually reduced over a time period T3, thereby effecting restoration actuation of the nozzle diameter. By setting suitably the levels of the voltages Vrev, Vop, the ink discharging amount (namely the recording dot diameter) can be varied. The minimum time interval for ink discharging is made, for example, the maximum 3 kHz of 333 .mu.s. Full color recording can be effected by the presence of respective driving of the energy generating member provided corresponding to ink path communicated discharge openings 41 to 44, control of the ink discharging amount, etc. Also, if the recording data D is letters data, recording of letter is also possible.
However, in such ink jet recording method of the prior art, which may be suitable for full color image by driving the energy generating member of the ink path corresponding respectively to the four colors, although printing only by black is necessary for recording of letter recording, the energy generating members in the ink path of other color are to be controlled, whereby no high speed printing could be performed. For example, in the case of performing recording one letter by 12 (dot).times.7 (dot), if superfluous time other than recording is disregarded, when driven at 3 kHz, about 36 letters (3000/(12.times.7)=36) can be recorded per second, which however cannot be said to be high speed printing, thus not satisfying the demand.